Commit 95f567f8 authored by Stefan Berger's avatar Stefan Berger Committed by Al Viro
Browse files

fs: Simplify getattr interface function checking AT_GETATTR_NOSEC flag 



Commit 8a924db2 ("fs: Pass AT_GETATTR_NOSEC flag to getattr interface
function")' introduced the AT_GETATTR_NOSEC flag to ensure that the
call paths only call vfs_getattr_nosec if it is set instead of vfs_getattr.
Now, simplify the getattr interface functions of filesystems where the flag
AT_GETATTR_NOSEC is checked.

There is only a single caller of inode_operations getattr function and it
is located in fs/stat.c in vfs_getattr_nosec. The caller there is the only
one from which the AT_GETATTR_NOSEC flag is passed from.

Two filesystems are checking this flag in .getattr and the flag is always
passed to them unconditionally from only vfs_getattr_nosec:

- ecryptfs:  Simplify by always calling vfs_getattr_nosec in
             ecryptfs_getattr. From there the flag is passed to no other
             function and this function is not called otherwise.

- overlayfs: Simplify by always calling vfs_getattr_nosec in
             ovl_getattr. From there the flag is passed to no other
             function and this function is not called otherwise.

The query_flags in vfs_getattr_nosec will mask-out AT_GETATTR_NOSEC from
any caller using AT_STATX_SYNC_TYPE as mask so that the flag is not
important inside this function. Also, since no filesystem is checking the
flag anymore, remove the flag entirely now, including the BUG_ON check that
never triggered.

The net change of the changes here combined with the original commit is
that ecryptfs and overlayfs do not call vfs_getattr but only
vfs_getattr_nosec.

Fixes: 8a924db2 ("fs: Pass AT_GETATTR_NOSEC flag to getattr interface function")
Reported-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Closes: https://lore.kernel.org/linux-fsdevel/20241101011724.GN1350452@ZenIV/T/#u


Cc: Tyler Hicks <code@tyhicks.com>
Cc: ecryptfs@vger.kernel.org
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: linux-unionfs@vger.kernel.org
Cc: Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarStefan Berger <stefanb@linux.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 0dd4fb73

fs/ecryptfs/inode.c

+2 −10
Original line number Diff line number Diff line
@@ -1008,14 +1008,6 @@ static int ecryptfs_getattr_link(struct mnt_idmap *idmap, 
	return rc;

}



static int ecryptfs_do_getattr(const struct path *path, struct kstat *stat,

			       u32 request_mask, unsigned int flags)

{

	if (flags & AT_GETATTR_NOSEC)

		return vfs_getattr_nosec(path, stat, request_mask, flags);

	return vfs_getattr(path, stat, request_mask, flags);

}



static int ecryptfs_getattr(struct mnt_idmap *idmap,

			    const struct path *path, struct kstat *stat,

			    u32 request_mask, unsigned int flags)
@@ -1024,7 +1016,7 @@ static int ecryptfs_getattr(struct mnt_idmap *idmap, 
	struct kstat lower_stat;

	int rc;



	rc = ecryptfs_do_getattr(ecryptfs_dentry_to_lower_path(dentry),

	rc = vfs_getattr_nosec(ecryptfs_dentry_to_lower_path(dentry),

			       &lower_stat, request_mask, flags);

	if (!rc) {

		fsstack_copy_attr_all(d_inode(dentry),

fs/overlayfs/inode.c

+5 −5
Original line number Diff line number Diff line
@@ -170,7 +170,7 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path, 


	type = ovl_path_real(dentry, &realpath);

	old_cred = ovl_override_creds(dentry->d_sb);

	err = ovl_do_getattr(&realpath, stat, request_mask, flags);

	err = vfs_getattr_nosec(&realpath, stat, request_mask, flags);

	if (err)

		goto out;
@@ -195,7 +195,7 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path, 
					(!is_dir ? STATX_NLINK : 0);



			ovl_path_lower(dentry, &realpath);

			err = ovl_do_getattr(&realpath, &lowerstat, lowermask,

			err = vfs_getattr_nosec(&realpath, &lowerstat, lowermask,

						flags);

			if (err)

				goto out;
@@ -248,7 +248,7 @@ int ovl_getattr(struct mnt_idmap *idmap, const struct path *path, 


			ovl_path_lowerdata(dentry, &realpath);

			if (realpath.dentry) {

				err = ovl_do_getattr(&realpath, &lowerdatastat,

				err = vfs_getattr_nosec(&realpath, &lowerdatastat,

							lowermask, flags);

				if (err)

					goto out;

fs/overlayfs/overlayfs.h

+0 −8
Original line number Diff line number Diff line
@@ -412,14 +412,6 @@ static inline bool ovl_open_flags_need_copy_up(int flags) 
	return ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC));

}



static inline int ovl_do_getattr(const struct path *path, struct kstat *stat,

				 u32 request_mask, unsigned int flags)

{

	if (flags & AT_GETATTR_NOSEC)

		return vfs_getattr_nosec(path, stat, request_mask, flags);

	return vfs_getattr(path, stat, request_mask, flags);

}



/* util.c */

int ovl_get_write_access(struct dentry *dentry);

void ovl_put_write_access(struct dentry *dentry);

fs/stat.c

+1 −4
Original line number Diff line number Diff line
@@ -165,7 +165,7 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat, 
	if (inode->i_op->getattr)

		return inode->i_op->getattr(idmap, path, stat,

					    request_mask,

					    query_flags | AT_GETATTR_NOSEC);

					    query_flags);



	generic_fillattr(idmap, request_mask, inode, stat);

	return 0;
@@ -198,9 +198,6 @@ int vfs_getattr(const struct path *path, struct kstat *stat, 
{

	int retval;



	if (WARN_ON_ONCE(query_flags & AT_GETATTR_NOSEC))

		return -EPERM;



	retval = security_inode_getattr(path);

	if (retval)

		return retval;

include/uapi/linux/fcntl.h

+0 −4
Original line number Diff line number Diff line
@@ -154,8 +154,4 @@ 
					   usable with open_by_handle_at(2). */

#define AT_HANDLE_MNT_ID_UNIQUE	0x001	/* Return the u64 unique mount ID. */



#if defined(__KERNEL__)

#define AT_GETATTR_NOSEC	0x80000000

#endif



#endif /* _UAPI_LINUX_FCNTL_H */